Left atrial function under exercise

The cardiac response to exercise is complex and involves changes in heart r ate, contractility, preload and afterload. In intact, apparently normal, pa tients the relaxed left atrium is less compliant than the left ventricle, t hus facilitating passive transfer of blood between the two chambers during diastole. It is speculated that left atrial passive properties may be stron gly influenced by the pericardium and surrounding tissues and that minor ch anges in left atrial pressure should have a considerable effect on the patt ern of blood flow entering the left atrium from pulmonary veins. Thus, it i s reasonable to expect that each of the functions of the left atrium may ch ange during exercise. Augmented left atrial booster function during exercis e is considered to be an important mechanism compensating for impaired earl y diastolic filling, thus optimizing cardiac performance. This increase is due to the combined effects of increased left atrial preload and presumably of increased sympathetic stimulation. Hence, left atrium size and systolic dysfunction are predictors of decreased exercise capacity and are associat ed with increased neurohormonal response.